Background: Psychotherapy is highly effective and widely acknowledged for treating various mental disorders. Nevertheless, in terms of methods for teaching effective psychotherapeutic approaches and competencies, there has been a lack of investigation. Training and supervision are the main strategies for teaching therapist competencies, and standardized role-plays with simulated patients (i.e., trained individuals playing someone with a mental disorder) seem useful for evaluating training approaches. In medical education, this procedure is now internationally established. However, so far, little use has been made of standardized role-playing to evaluate training and supervision in the area of clinical psychology and psychotherapy.Methods: In this study, standardized role-plays are used to evaluate methods for training and supervision. Central cognitive behavioral approaches for treating depression are taught in the training. The first experiment compares an active training approach (i.e., model learning) with a passive one (i.e., reading manual-based instructions). The second experiment compares a direct supervision technique (i.e., supervision based on video analysis) with an indirect one (i.e., supervision based on verbal reporting). In each experiment, 68 bachelor's and master's students of psychology will be randomly assigned to the experimental and control groups. Each student takes part in three role-plays (baseline, post and 3-month follow-up), which are all videotaped. Two independent raters assess therapist competencies in each role-play on the basis of a standardized competence scale.Discussion: The research project aims to contribute to the development of specific training and supervision methods in order to improve psychotherapy training and patient care.